My perspective is off

Sitting at a bar, passing a few minutes before arriving at a party for which I’m unfashionably early (a friend’s son’s bar mitzvah), I’m sitting next to a party of three – two attractive young women, and an attractive young man. They were here before I arrived, but I’m kinda shocked they’re legal. I’d have guessed 19. Maybe 20. No way 21. Anyway, turns out, one of the chicks is engaged – they’re celebrating. And interactions reveal they’re late 20s/early 30s. I’m old.